No problems were reported at any of the nuclear plants in the area, although none of them are in operation.

Earthquakes are common in Japan, one of the world's most seismically active areas, which accounts for a fifth of the world's earthquakes of magnitude 6 or larger.

Japan's strongest quake on record was one of magnitude 9 that struck the northeast coast on March 11, 2011, unleashing a massive tsunami and killing nearly 20,000 people, besides setting off the world's worst nuclear crisis since Chernobyl.

Thursday's quake came roughly two months after a major earthquake hit the southernmost island of Kyushu and killed 49 people.